In what seems like a radical but somewhat logical move, it is increasingly looking like Microsoft is talking away the ability to join a Windows domain from the core or baseline versions of Windows 8.
This is a pretty big change for Windows.
In addition, the word on the street is that the Remote Desktop functionality will also be removed from the baseline version.
Some screenshots from the Winunleakedforums.tk.
Notice the grayed out Network ID button in the Windows 8 Pro version.